[i]I don't know, what are the advantages to mulching it. alot of the customers believe that bagging is the way, what are my selling points goin to be? [/B]

Wow, that's alot of grass to bag and remove! Everything I've read says that mulching is the way to go. The small, mulched grass clippings break down and are good for the lawn. I'd find something on the net, or a book (Ortho has a book on "Lawns". It's part of a whole series of books they make), and show it to the customers if they don't seem to buy it when you tell them.
As someones else already mentioned, check with your local municipality to see if they have some sort of information packet. Heck, I seem to even recall commercials on tv when I was younger promoting mulching over bagging.